Prefabricated structural unit and method

ABSTRACT

The prefabricated structural unit disclosed herein includes a metal frame or skeleton formed of a plurality of steel studs or channels welded into a shaped unitary frame having the general exterior configuration of the structural unit. Asbestos-cement panels or sheets are permanently secured to the exterior of the frame which are joined and sealed by an adhesive to form a continuous monolithic exterior surface. The exterior surface is then finished by coating the surface with a cementitious matrix into which is distributed a stone or other aggregate providing a precast monolithic appearance. The disclosed method of forming a prefabricated structural unit includes welding the steel channels or studs into a relatively lightweight unitary frame structure, permanently securing the asbestos-cement panels over the exterior of the frame, as by nailing the panels directly to the frame, and joining and sealing the panels with an adhesive. A cement matrix is then applied over the panels and a stone aggregate is distributed in the matrix while the matrix is in the fluid state. The exterior surface is then dried, wherein the cementitious matrix forms a substantially continuous layer with the cement-asbestos panels.

[ 1 Dec. 25, 1973 1 i PREFABRICATED STRUCTURAL UNIT AND METHOD [75] Inventor: Cornelis J. De Lange, Farmington,

Mich.

[731 Assignee: Cement Enamel Development, Inc.,

Detroit, Mich.

[22] Filed: Jan. 26, I972 [21] Appl. No.: 220,854

[52] US. Cl 52/309, 52/311, 52/315 [51] Int. Cl. B44f 9/04, B44f 7/00 [58] Field of Search 52/34, 315, 364, 52/434, 309, 344, 433, 447

[ 56] References Cited UNITED STATES PATENTS 1,502,603 7/1924 Walper 52/443 3,315,424 4/1967 Smith 52/309 3,243,930 4/1966 Sl0winski.... 52/364 3,245,185 4/1966 Rowe 52/364 3,341,797 9/1967 Pestel 52/364 3,471,184 10/1969 Hayes 52/309 3,621,635 11/1971 De Lange 52/315 FOREIGN PATENTS OR APPLICATIONS 202,129 8/1923 Great Britain 52/344 OTHER PUBLICATIONS Stucco Textures and Finishes,'by Bacholtz, pages ii 21,22,24.

Primary Examiner.lohn E. Murtagh Assistant Examiner-Henry C. Raduazo Attorney-Raymond E. Scott [5 7] ABSTRACT The prefabricated structural unit disclosed herein includes a metal frame or skeleton formed of a plurality of steel studs or channels welded into a shaped unitary frame having the general exterior configuration of the structural unit. Asbestos-cement panels or sheets are permanently secured to the exterior of the frame which are joined and sealed by an adhesive to form a continuous monolithic exterior surface. The exterior surface is then finished by coating the surface with a cementitious matrix into which is distributed a stone or other aggregate providing a precast monolithic appearance.

The disclosed method of forming a prefabricated structural unit includes welding the steel channels or studs into a relatively lightweight unitary frame structure, permanently securing the asbestos-cement panels over the exterior of the frame, as by nailing the panels directly to the frame, and joining and sealing the panels with an adhesive. A cement matrix is then applied over the panels and a stone aggregate is distributed in the matrix while the matrix is in the fluid state. The exterior surface is then dried, wherein the cementitious matrix forms a substantially continuous layer with the cement-asbestos panels.

5 Claims, 7 Drawing Figures PREFABRICATED STRUCTURAL UNIT AND METHOD FIELD OF THE INVENTION The structural unit and method of this invention relate to prefabricated structural units or modules which may be utilized in commercial and residential building structures. The preferred structural embodiment has the appearance of a precast structural unit, but which may be manufactured and assembled away from the building site.

The substantial increases in construction and building costs are well known. These increases are due in large part to the increases in the cost of skilled labor, which is now expensive and in short supply. Concrete block walls are prone to structural cracks. Brick-block construction is time consuming and costly, and precast concrete is extremely expensive and adds tons of design weight to the final structure. A prefabricated exterior wall structure should be composed of noncombustible, modular lightweight units. On one-story structures, for example, wall units should be capable of supporting roof joist loads, and on multiple-story projects, the modular units must meet fire and wind load requirements and permit easy anchorage to adjacent support structure. The exterior finish of the modular units preferably provide some versatility in the texture of the exterior wall and the units are preferably easily assembled, without heavy erection equipment.

The disclosed embodiment of the prefabricated structural unit and method of this invention substantially reduces the deadload. Most embodiments weigh less than pounds per square foot, while equivalent precast concrete or masonry sections weigh at least five times that amount. The disclosed structural unit creates a thin, easy to insulate wall system with built-in support for the interior wall finish material.

The prefabricated structural unit of this invention may be made up entirely of noncombustible components, including steel studs, cement asbestos board and cement-based surfacing. The units qualify for use in Class A structures. The improved structural unit of this invention offers substantial cost savings over precast concrete or conventional masonry exterior wall systems. The lightweight structural unit not only permits substantial design savings but allows quick and easy installation at the construction site, which results in substantial field labor savings. The relatively thin strong structural units create more usable floor space in the final structure and eliminate the need for separate interior furring supports.

Finally, the improved prefabricated structural unit and method of this invention results in a freedom of design which is not available in other systems. The entire system is extremely versatile, permitting an almost unlimited number of design configurations and almost any surface finish. The lightweight structural units may be prefabricated many miles from the construction site, shipped by available means and erected quickly and easily.

The prefabricated structural unit of this invention includes a support frame or skeleton which is preferably formed of a plurality of steel studs or channels welded into a shaped unitary frame. The frame may be formed of a plurality of modular frame units wherein each frame unit includes three vertical studs and two cross members which are welded into a modular frame unit.

The frame units are then welded together, as required by the specific application and braced, as required. The exterior configuration of the frame conforms to the general exterior shape of the prefabricated structural unit.

The exterior of the frame is then covered with asbestos-cement panels which are permanently secured over the frame structure. The panels may be secured directly to the frame by self-locking nails or screws, for example. The panels are then joined and sealed by a suitable adhesive which forms a continuous exterior surface. This surface is then finished by applying a cementitious matrix material over the panels and distributing, within the matrix, an aggregate exterior surfacing, such as chipped stone or the like. The fluid cement matrix will form a substantially unitary exterior layer with the panels, forming an extremely, strong, lightweight prefabricated structural unit which has the appearance of precast concrete without the disadvantages of such a system.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a typical embodiment of the prefabricated structural unit of this invention;

FIG. 2 is a perspective view of the assembly frame utilized in the structural unit shown in FIG. 1;

FIG. 3 is a partial perspective view of the frame and assembly; and

FIGS. 4 to 7 illustrate various steps in the method of manufacturing the prefabricated structural unit shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates one of the many possible embodiments of the prefabricated structural unit which may be developed with the method of this invention. The disclosed embodiment of the structural unit 20 is a two story prefabricated module or unit which has the appearance of a precast concrete or masonry section, but which is relatively inexpensive, substantially lighter in weight and which may be prefabricated away from the building site in a factory.

The disclosed structural unit may be easily anchored to the supporting structure 22, which may also be prefabricated as described herein. The disclosed structural unit includes a plurality of vertical columns 24, a plurality of prefabricated window units, such as shown at 26, and the disclosed embodiment is shaped to include horizontal beams 28 and 30 and inclined faces 32. It will be understood that the shape and appearance of the prefabricated structural unit of this invention is a matter of design, however it is also important to note that the disclosed structure and method of this invention is particularly versatile.

FIG. 2 illustrates one embodiment of the frame assembly 34 suitable for supporting the prefabricated structural unit 20 shown in FIG. 1. The disclosed embodiment of the frame assembly includes a plurality of prefabricated frame units or modules 36 and 38. Frame sections 40 and 42 may also be prefabricated by welding or otherwise securing the individual studs or channels. The frame modules are then braced, as required for the particular application. In the disclosed embodiment, the braces 44 also form the skeleton for the inclined faces 32, as shown in FIG. 1.

The frame modules 36 and 38, in the disclosed embodiment of the frame assembly, include three vertical studs 46 and two horizontal beams 48. The studs and channels in the preferred embodiment of the frame assembly are steel or other suitable metal and are welded, as at 50, into a unitary structure. The individual modules are then welded together, as at 52, to provide a strong, relatively light-weight skeleton for the structural assembly. It will be noted that the exterior of the frame assembly generally conforms to the desired shape of structure. For example, the structural units 40 and 42 support the inclined faces 32 and the modules 38 provide the vertical columns 24.

After forming of the skeleton or frame 34, the exterior surface of the frame is covered with panels or sheets 56, as shown in FIG. 3. The panels are preferably formed of a cementitious material, such as the commercially available asbestos-cement panels manufactured and sold by .lohns-Manville under the trade name FLEXBOARD. Other suitable cementitious panels are also available commercially. The panels are preferably secured directly to the steel channels or studs, as shown in FIG. 3 at 58. The panels may be secured by selflocking nails, screws, or the like. The panels are then joined and sealed by a suitable adhesive or caulking, as shown at 62 in FIG. 4. This section is taken through the module 40 in FIG. 2, wherein the panels are secured directly to the braces 44 and the horizontal beam 40. A suitable adhesive-caulking is a conventional epoxy resin adhesive, which is relatively shrink resistant and seals the adjacent panels.

The panels are then covered with a viscous fluid matrix 68, as shown in FIG. 5. The preferred matrix material is a cementitious material of a similar composition to the panels 56, such that the matrix and panelbecome substantially a unitary structure in the final assembly. A suitable matrix material includes Portland Cement, sand and a resin binder, such as a water soluable acrylic resin. Other cement or cement-asbestos matrix materials may also be utilized. It will be noted that the matrix material is preferably sprayed on the panels, such as shown at 70 in FIG. 5, to provide a continuous monolithic exterior surface which covers the fastening means 58 and provides a particularly pleasing appearance. Finally, the surface 68 is covered with an aggregate material, such as shown at 72 in FIGS. 6 and 7 which provide the appearance of precast concrete or masonry. A suitable aggregate material is crushed stone, such as quartz, which provides a very satisfactory coating for the structural unit. Other aggregate materials may also be utilized.

It will be noted from the above that the finished structural unit is fabricated from exclusively noncombustible, relatively lightweight structural elements. The lightweight structural unit of this invention not only permits substantial design savings, but also allows quick and easy installation at the construction site and results in substantial field labor savings. Other advantages of the structural unit and assembly of this invention are described hereinabove.

I claim:

1. A prefabricated structural unit, comprising: a selfstanding support frame formed of a plurality of modular rectangular frame portions, each frame portion having vertical and horizontal steel studs welded together into a rigid structure and said rectangular frame portions stacked vertically and welded together into a unitary self-supporting frame having the general external configuration of the structural unit to be formed, asbestos-cement panels overlying the shaped exterior of said frame and permanently secured thereto, said panels joined and sealed together by an adhesive to form a continuous monolithic exterior surface, and a stone aggregate exterior surface on said exterior surface of the panels retained thereon by a cement matrix, said matrix having substantially the same composition as said panels and forming a unitary exterior layer integral with said asbestos-cement panels, permanently bonding said stone aggregate and thus forming a unitary exterior structural unit.

2. The prefabricated structural unit defined in claim 1, characterized in that said asbestos-cement panels are directly secured to said frame by nails.

3. The prefabricated structural unit defined in claim 2, characterized in that said panels are joined and sealed by a catalized epoxy resin adhesive caulking which permanently joins and seals the adjacent panels.

4. The prefabricated structural unit defined in claim 1, characterized in that said support frame is formed of a plurality of prefabricated modular frame units each having three vertical stud members welded together by opposed cross members.

5. The prefabricated structural unit of claim 1 and including:

said frame including studs in each of two perpendicular planes and studs in a third plane intersecting said two perpendicular planes, and

said asbestos-cement panels overlying the studs in said perpendicular planes and overlying the studs in said third plane to form an inclined surface. 

1. A prefabricated structural unit, comprising: a self-standing support frame formed of a plurality of modular rectangular frame portions, each frame portion having vertical and horizontal steel studs welded together into a rigid structure and said rectangular frame portions stacked vertically and welded together into a unitary self-suppOrting frame having the general external configuration of the structural unit to be formed, asbestoscement panels overlying the shaped exterior of said frame and permanently secured thereto, said panels joined and sealed together by an adhesive to form a continuous monolithic exterior surface, and a stone aggregate exterior surface on said exterior surface of the panels retained thereon by a cement matrix, said matrix having substantially the same composition as said panels and forming a unitary exterior layer integral with said asbestoscement panels, permanently bonding said stone aggregate and thus forming a unitary exterior structural unit.
 2. The prefabricated structural unit defined in claim 1, characterized in that said asbestos-cement panels are directly secured to said frame by nails.
 3. The prefabricated structural unit defined in claim 2, characterized in that said panels are joined and sealed by a catalized epoxy resin adhesive caulking which permanently joins and seals the adjacent panels.
 4. The prefabricated structural unit defined in claim 1, characterized in that said support frame is formed of a plurality of prefabricated modular frame units each having three vertical stud members welded together by opposed cross members.
 5. The prefabricated structural unit of claim 1 and including: said frame including studs in each of two perpendicular planes and studs in a third plane intersecting said two perpendicular planes, and said asbestos-cement panels overlying the studs in said perpendicular planes and overlying the studs in said third plane to form an inclined surface. 